The present invention relates to a hydraulic unit and at least two hydraulic connections or fittings connectable with the hydraulic unit through a security connection system.
The invention is applicable to any hydraulic or fluid system and is particularly suited for use in the actuating hydraulic system for a thrust reverser of a bypass fan type turbojet engine where the thrust reverser must meet the highest standards of reliability.
It is well known in this type of application that the bypass fan engine is provided with a duct at the rear of the fan to channel the so-called cold, bypass flow. This duct consists of an inner wall which encloses the exterior of the engine core and of an outer wall which at its forward end is continuous with the fan housing. This outer wall may channel both the bypass flow and the so-called hot, primary flow exhausting from the rear of the jet engine (in which case the hot and cold flows may be either mixed or confluent), or may channel only the bypass flow when so-called separate flows are involved.
In addition, a wall may fair the engine exterior surface, that is, the outside surface of the housing which surrounds the fan, to the exterior surface of the outer wall of a bypass duct like that described above in order to minimize powerplant drag. This is the case especially for powerplants affixed to the exterior of an aircraft, in particular when these powerplants are attached under the wings or mounted to the rear of the fuselage.
The thrust reverser used with a fan type turbojet engines may be one several known types such as a door type reverser, a cascaded type reverser or the so-called "target" type reverser which is fitted with aft deflector panels. Generally, the moveable elements of these thrust reversers are driven by a hydraulic unit (also called a HCU or Hydraulic Control Unit) connected or associated with hydraulic linear actuators which directly effect the movement and locking of the elements of the thrust reverser. FIG. 1 of the attached drawings shows a known embodiment of such a hydraulic unit that includes a hydraulic circuit supply connector or fitting 14 and a hydraulic circuit return connector or fitting 15. In the known embodiments such as that shown in FIG. 1, the fluid supply hose or conduit and its associated connector 14 and the fluid return conduit and its associated connector 15 are physically separate from each other.
During maintenance, the supply and return conduits of the fluid circuit may be disconnected from the hydraulic unit at which time stoppers are used to protect the connectors. This presents the danger that the mechanic may reconnect the supply connector while forgetting to reconnect the return connector and leaving the stopper on the return connector. Should the engine be returned to service in this condition, the pressure in the hydraulic circuit may become excessive and cause operational difficulties.
It has been proposed in the prior art to design apparatus to prevent the hookup of a hydraulic supply conduit in the absence of the hookup of a return or discharge conduit such as, by way of example, the arrangement shown in connection with the filling means in the European patent document A 0,494,818 (U.S. Pat. No. 5,251,818).